Target selector and comparator circuits



Dec. 15, 1964 N. c. OLMSTEAD TARGET SELECTOR AND COMPARATOR CIRCUITS Filed Jan. 21, 1955 67325.13 E zoiumniou INVENTOR. N.C. OLMSTEAD fidc fl United States Patent Ofiice 3,161,76ti TARGET SELECTOR AND COMPARATOR CIRCUITS Noel C. Olmstead, Whippany, NJL, assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Jan. 21, 1955, Ser. No. 483,447 6 Claims. (G. 23561.5)

This invention relates to a circuit means for selecting and comparing target information and more particularly to circuit means capable of finding targets assigned to director-trackers having the largest closing time, or least threat, in a fire control system and comparing these assigned targets with unassigned targets to consider the targets of greatest threat for the director-trackers.

In one fire control system, of which this invention is a part, a plurality of targets with respect to a station, as an aircraft, ship, or the like, are evaluated by their respective threats usually in terms of closure time, or time that it would take an approaching target to collide with the station. The target may be another aircraft, ship, or the like. A limited number of targets, and particularly those which appear to be within range of the defensive weapons in use, are assigned to and therefore tracked by director-trackers, as radars, from which firing intelligence is computed for defensive guns. For movable targets the threat of the limited assigned or tracked targets as well as the unassigned or untracked targets may change momentarily necessitating a constant re-evaluation of the tracked and untracked targets for director-tracker assignment.

In the present invention a circuit combination is shown and described for finding or selecting the assigned targets having maximum closing time and for comparing the maximum closing time less handling time of these assigned targets with the closing time of threatening unassigned targets in order that the targets of greatest threat are always being tracked for gun firing orders. Where, by comparison, an unassigned or untracked target is found to be a greater threat than an assigned or tracked one, a circuit switch is controlled preparatory to taking the director-tracker away from the previously tracked target and directing it to the new target. Whilethe description and drawing disclose circuit means for threeassigned targets, such disclosure is for illustrating the invention only and a, plurality of targets more than three may be assigned, where desired. It is therefore a general object of this invention to provide a circuit for evaluating the closure time of a plurality of known targets as represented in electrical potentials and comparing these with the closure time of new targets whereby rearrangement of director-tracker and gun assignments may be made to provide protection against targets of greatest threat. These and other ob jects, advantages, features, and uses will become more apparent as the description proceeds when considered along with the accompanying drawing showing a schematic circuit of the invention. i v

Referring to the drawing, the circuit of this invention includes several network and relay components. Each network is set off in dotted lines and the several networks and relays are identified, in general, by legends. Thesevdirect current (D.C.) amplifier 14, a clamping network 15, a .1 D.C. amplifier network 16, anda-Comparator 17 for channel (A). The components 10, 11, 13, 14, 15 and 16 are each used as a single unit in this invention whilethe components 12 and 17 are duplicated to the extent of .the number of channelsainthe system andnare coupled into'the circuit as indicated in the drawing by 3,161,763 Patented Dec. 15, 1964 leads to channels (B) and (C). While the drawing shows these leads to channels (B) and C), it is to be understood that additional channels may be incorporated, where desired.

Finder Sweep The Finder Sweep generator 10 provides a negative sweep voltage which is generated across a condenser 20 of aresistor 21-condenser 20 combination connected from a positive voltage to a negative voltage, as +300 to 300 D.C. volts. The condenser 20 is normally shorted by the normally closed contacts 22 of a Start Finder relay SF which also has normally closed contacts 23- and normally open contacts 24. The fixed contact of the contacts 23 is grounded. In parallel to the condenser 20 is a gas-filled tube 25, such as a thyratron, which has the anode thereof connected through a normally closed con tact 26 of a two-pole Recycle Finder relay. A normally open contact 27 of this relay is connected to the negative voltage to be capable of also shorting out condenser 20 when this relay is energized. When the short across the condenser 20 through the SF relay contacts 22 is removed, the condenser starts charging to produce a sweep voltage in the anode circuit of the tube 25 starting, for example, at 300 volts which will rise to rear +300 volts, if not stopped, the operation of which will later become clear as the description proceeds.

Monitor Finder The positive side of the condenser 20' is also coupled to the input of the Monitor Finder network 11 through a conductor 29. The input to the network 11 is to the grid of an amplifier tube 36' the output of which is connected to the grid of a gas filled tube 31, as a thyratron. The anode of the tube 31 is coupled through the energization coil of a monitor finder relay MF and through the normally closed contacts 32 of a resetting relay RS. The MF relay has three switch contacts 33, 34, and 35, the switch blade of each being grounded with the switch contacts 3-3 and 35 being normally open and the switch contacts 34 being normally closed. The fixed contact of the switch contacts 33 is connected by a conductor 36 to the switch blade of SF relay switch contacts 23 and also to the windings of unassigned target signal (UTS) relays, only that for channel (A) being shown. The fixed contact of switch contacts 34 is connected by a conductor 37 to the switch blade of the SF relay contacts 24. The fixed contact of the switch contacts 35 is connected by a conductor 38 through the energization coil of the Recycle Finder relay to a voltage source in one path'and through the energization coil of the RS relayto a voltage source in a second path. The function of the network 11 is dependent 'on the other components of the circuit and this function will be more fully explained with the coming description.

' Finder (A) The Finder network-12 includes a double triode amplifier tube 40 having its output coupled to a gas filled tube 41, as a thyratron. As an input to the first grid offthe tube 40, the anode of the tube 25 in the network 10 is coupled by conductor 42 through a resistor 43, and a closure time computer of an assigned targetcf channel (A) (not shown) is coupledthrough a resistor 44 to this grid. The voltage. from the condenserZD-sweeps, for example, from -300volts to +300 volts, as herein-- before described, and the voltage from the closure time condition o-tnegative potential, or negative vbias, on the grid of the thyratron 41. This negative bias is gradu ally overcome by the positive signal from amplifier 40 and as the bias reaches zero, tube 41 conducts. The sweep voltage from the network is coupled likewise to the Finder networks of channels (B), (C), etc., as shown. The anode of tube 41 is coupled through a resistor 46 by a conductor 47, through the energization coil of a relay F(A), and through the normally closed contacts 48 of a storage relay SG(A) to a B+ voltage source. The anode of tube 41 is also coupled in. a parallel path by the conductor 49 to the B-lvoltage source, being tapped into the conductor 47 between the SG(A) contacts 48 and the energization coil of the relay F(A). The cathodes at the tubes 41 in all channels are connected by a conductor 42' to the grid of tube 25 with a resistor R in common ground thereto.

The relay F(A) has four normally open switch contacts 50, 51, 52, and 53. The switch blade of switch contacts 50 is grounded. The fixed contact of the contacts 50 is coupled by conductor 54 to the energization coil of the Recycle Finder relay in network 10 and through the energization coil of a relay 60 in the Time Out Gate network 13, soon to be described. The conductor 54 is also connected to the corresponding fixed contact in channels (B), (C), etc. The switch blade of contacts 51 is connected to ground through the switch contacts 61 of another relay 62 in the network 13 and is also connected to corresponding switch contacts in channels (B), (C), etc. The fixed contact of the contacts 51 is coupled to a voltage source through an energization holding coil of the relay F(A) and through the energization coil of the storage relay SG (A). This voltage source is also connected through an energization holding coil of the SG(A) relay through normally open contacts 55 thereof to the fixed contact of the SF relay contacts 24 via conductor 56. The fixed contact of the SG(A) contacts 55 are all connected in parallel to the corresponding contact of the SG relays in channels (B), (C), etc. The fixed contact of the F(A) contacts 52 is connected to ground through the relay contacts 61 the same as the switch blade of contacts 51. The switch blade of the contacts 52 is connected by conductor 57 to the corresponding part in channels (B), (C), etc. and to a voltage source through the energization coil of a start comparator relay SC. The fixed contact of the F(A-) contacts 53 is connected to the output signal of the channel (A) closure time computer for an assigned target (not shown) and the switch blade of these contacts is connected to a conductor 58 which is an input to the +1 D.C. amplifier network 14, soon to be described.

Time Out Gate The relay 60 in the Time Out Gate network 13 has a normally closed and a normally open set of contacts 63 and 64, respectively. The contacts 63 operate to open a resistance-capacitance circuit 65 which R-C circuit is coupled to the grid of a gas-filled tube 66, as a thyratron. The normally open contacts 64 are capable, when closed, to supply a B+ voltage to the anode of the tube 66 through the energization coil of the relay 62. The R-C circuit 65 is' designed to cause a delay in the operation of the relay 62 for a period of time sutficient to allow other components of the system to complete their functions, :aswill later be made clear. The point of firing of the tube 66 can be controlled within limits by the adjustable grid bias 67.

+1 D.C. Amplifier The potential representative of the closure time of an assigned target in channel (A), which potential by closure time computer design is positive and does not exceed 100 volts, is fed into the first grid of two double triode tubes 70 and 71. It is to be noted that this first grid of tube 70 also has the potentials representative of closure time from channels (B), (C), etc. fed into it so that all channels will be considered. Amplification can be controlled by the potentiometer 72 coupled to the last grid of the triode 71. The output voltage is taken from the first anode of the triode 71 via conductor 73 and this voltage is equal to the closing time of the selected assigned target.

Clamping Circuit The conductor 73 is passed through a clamping circuit 15 having germanium crystal rectifiers 75 therein. A sweep voltage provided by resistor-capacitor 76-77 circuit coupled between a voltage source and ground has the conductor 73 connected between the resistor 76 and capacitor 77 so that the sweep voltage is clamped at the maximum voltage of the selected assigned target. The output of the clamped sweep voltage is by conductor 78 one branch of which is normally grounded through normally closed contacts 79 of the SC relay. The sweep voltage source is capable of going higher than the maximum voltage of the selected target, as +300 volts for example.

-1 Summing Amplifier The clamped sweep voltage is fed via conductor 73 as one input to a 1 DC. Summing Amplifier network 16. This amplifier consists of a. plurality of tubes herein illustrated as three double triodes 8t), 81, and 82 coupled in the usual manner to amplify the sweep voltage up to the clamped voltage. Another input to this amplifier is a negative voltage from a potentiometer 83 which is manually adjustable to fix a voltage representative of handling time, or the time considered necessary for the fire control system, of which this circuit is a part, to compute, assign directors and guns, etc. The input of the sweep voltage sweeping from a 0 value upwards of a positive voltage will have deducted from it the handling time negative voltage providing an output voltage equal in magnitude to the closing time of the selected target minus the handlingtime. The output of this 1 amplifier, as well known in the art, reverses the polarity of the input thereto whereby the closing time of the selected assigned target is represented as a negative value at the output thereof.

Comparator (A) The output of the network 16 is by the conductor 84 which is fed into the comparator networks of all the channels, the Comparator (A) being shown herein as network 17 to illustrate the invention. The comparator network 17 includes a DC. amplifier 9t) and a gas filled tube 91, as a thyratron, coupled in circuit. The amplifier is a double triode the first grid of which has two inputs, one input being by conductor 84 from the network 16 and the other input being from the closure time computor of the corresponding channel (A) for an unassigned target. The two input voltages are constantly summed through resistors 92 and 93 and as the sweep voltage value approaches in the negative direction the value of the positive voltage representative of the closure time, which will not exceed 100 volts, for the unassigned target the net voltage will pass through 0.. The network 17 is designed to fire the tube 91 when the net input voltage passes through zero, the point being adjustably selected by the control of the second grid of the triode 90 through the potentiometer 94. The circuit of the comparators differ from that of the finders in that the DC. amplifier 90 is reversed so that the grid of the tube 91 is held negative by a positive rather than a negative net input voltage. A B+ voltage for the anode of the tube 91 is supplied through normally open contacts 95 of the SC relay, through the energization coil of a target exclusion relay generally referred to by the legend TXE(A), and through normally open contacts 96 of an unassigned target signal relay, generally referred to by the legend UTS(A). The TXE relays for channels (B), (C), etc. are connected to the output side of the 'SC relay contacts 95 so that all comparators may be operative where the related UTS relay indicates that the respective channel has an unassigned target to. consider. Whenever Comparator (A) is operated as by the firing of the tube 91, showing that the closure time of the unassigned target is less than the closure time less handling time of the assigned target in this channel, the TXE(A) relay will operate to control switches (not shown) to take the as signment of the presently assigned target away from the units involved in tracking and directing guns on the assigned target preparatory to the assignment of the unassigned target in this channel.

Operation In the operation of the circuit, the various relays will remain as shown until one of the UTS relays for the several channels operate. In the static condition, the network cannot start a sweep voltage because the condenser 20 is shorted out. The network 11 is likewise inactive because the input thereto cannot rise while the condenser 20 is shorted out. The network 12 is inactive in the absence of a sweep voltage. The network 13 can only start operating when one of the F relays is operated. The input to the network 14 is broken by the F relay and the sweep voltage through the R-C circuit 76-77 is grounded through SC relay contacts 79. The network 14 and sweep voltage being cut oil the networks 16 is inactive, and the anode circuit for the network 17 is broken at the SC relay contacts 95 and the UTS relay contacts 96.

The UTS relays for all channels, only UTS(A) relay being shown, are capable of operation by a circuit to ground through their windings (only UTS(A) being shown) being through the normally closed contacts 23 of the start finder relay SF. Upon the actuation of any UTS relay indicating that an unassigned target has appeared in some channel, the cycle will be started to compare the closure time of that unassigned target with the closure time (less handling time) of the assigned target having a maximum closure time. The closure time is computed from radar range and range rate by closure time computers which constitutes the subject matter of another application. For the purpose of example let it be assumed that the new unassigned target has appeared in channel (A) whereupon the UTS (A) and SF relay will be energized. The short is removed from condenser 20 in network 10 whereby the voltage builds up from the negative potential, as 300, starting a sweep which is summed with the potential, which does not exceed 100 volts, representative of the closure time of an assigned target in all channels. The channel having the assigned target with the maximum closurejtime will be the first to firethe tube 41 of the channel network 12. Let it beassumed here, for the purpose of example, that the assigned target in channel (A) had the target of maximum closing time causing tube 41 to fire energizing relay F(A) and blocking further sweep from network 10 by the voltage developed across resistor R to fire tube 25 shorting condenser 20. F(A) energization closes contacts 50, 51, 52, and 53 which breaks the sweepvoltage of the network 10 by voltage of network 14 representative of the assigned target closure time. This rising sweep voltage is fed into network 16 where the handling time is deducted therefrom and the result passed into the network 17 where it is compared withthe closure time voltage of the unassigned target. The output of network 16 will bea positive voltage equal in magnitude to the voltage representing handling time and as the sweep voltage starts the output voltage will decrease and go to a maximum negative value which will be equal in magnitude to the closing time of the selected assigned target less handling time. When the magnitude of the negative voltage from the network 16 reaches the magnitude of the positive voltage from the unassigned target closure time source, tube 91 will fire as the summed input voltage through the resistors 92 and 93 attempts to pass through 0. Firing of tube 91 energizes the TXE(A) relay which starts the process of excluding the assigned target in (A) channel and assigning the unassigned target in (A) channel, this process being the subject matter of another application.

No attempt is made to stop the sweep when one comparator network 17 operates as it is desired to let all unassigned targets which have a closing time less than that of the assigned target have a chance at the assigned targets director-tracker. However, it should be noted that as the sweep goes from 0 to a negative value, the comparator having the smallest value of closing time will be the first to operate and hence will have a head start to try for a director change.

It is also to be noted that these cycles actually operate very rapidly, the cycle time being in the order of approximately three milliseconds.

If the assigned target closure time less handling time, represented by the negative value at the output of network 16, is less than the unassigned target closure time, represented by a positive voltage, the summed voltage will never reach 0 and the tube 91 will never fire whereby the assigned target remains assigned in target channel (A).

The cycle of assigned target selection of maximum closing time and of comparison of this assigned target with the unassigned target is completed when the Time Out Gate network 13 has completed its delay function as determined by the RC circuit 65. After a predetermined interval of time greater than the time necessary for the networks 12, 1 15, 16, and 17 to complete their functions, the tube 66 will fire breaking the holding circuit through F(A) which allows the contacts 59, 51, 52, and 53 to return to their normally open positions completing the cycle of finding and comparing the first unassigned target.

It should be noted that the SG(A) relay of the target channel determined as having maximum closing time in the first cycle is still held by its holding circuit which excludes this target from consideration on the next cycle.

The relase of the F(A) relay releases the Recycle Finder relay which removes the short on thecondenser 20 allowing the Finder Sweep" network 10 to start anew sweep voltage. The sweep selects from the remaining finders (B), (C), etc. the one having the maximum closing time voltage and the unassigned targets are compared to the assigned target as set forth in the description of operation above. The cycle is repeated until the comparison has been made for each assigned target.

-After the comparison has been made with the last assigned target channel, the network 13-releases the'last F relay and the Recycle Finder relay and the finder sweep voltage is again started. This'time, since all assigned target finders are locked out by-the operation of-their SG relays; the finder sweep continues to rise to 0 volts where the monitor finder network 11 is operated. The operation of the Monitor Finder, MF, relay operates the Recycle Finder relay to reset the sweep to its negative value by shorting the condenser 26; releases all 86 relays bybreaking the holding circuit through contacts 34; puts a ground on the windings of the UTS relays so that any targets which have appeared as unassigned in the system will be considered in the next cycling period; and operates the RS relay which restores the network 11 for its next operation. The circuit is then ready to start a complete new principal cycle of operation of the finders and comparators to avoid or reassign new targets.

While the present description and illustration is a preferred form of the invention it is to be understood that many modifications and changes may be made in the constructional details and features as shown and described without departing from the spirit and scope of the inventive concept and I desire to be limited only by the scope of the appended claims.

I Claim: 7

1. In a multiple target gun fire-control system, wherein targets are selected on the basis of the closing-time between the gun and the target, the combination of means for producing a voltage representative of each target under consideration, the amplitude of each voltage being indicative of the closing-time between a particular target and the gun;

means for comparing the amplitude of said voltages,

and

means for selecting the voltage with the smallest amplitude, thereby indicating which of the targets under consideration has the smallest closing-time.

2. In a gun fire-control system capable of tracking a plurality of targets and detecting additional targets, the combination of a plurality of channels equal in number to the number of targets which the system is capable of tracking;

means in each channel to provide a signal representative of the closing-time of a particular target;

a first sweep generator having an output signal the value of which varies over the entire range of possible closing-time signals;

finder means in each channel responsive to the sweep signal and to the closing-time signal in that channel to produce a finder signal indicative of which channel represents the target having the greatest closingtime;

a second sweep generator;

means responsive to a finder signal in any channel to block the output of the first sweep generator and to initiate the operation of the second sweep generator;

further means responsive to a finder signal in any channel to limit the sweep range of the second sweep generator to a magnitude corresponding to the closing-time signal in that channel;

means to provide signals representative of the closingtime of any detected but untracked targets; and

comparison means responsive to the closing-time signals of such untracked targets and to the second sweep signal to provide an output signal if the closing-time signal of any untracked target represents a closing-tme less than that corresponding to the limiting level of the second sweep generator.

3. The system of claim 2 wherein the first sweep generator operates cyclically providing a sweep of negativeto-positive voltage;

the finder means and the comparison means both provide output signals when the summation of the respective signals applied thereto is zero, and further including monitor means to initiate a new cycling sequence of the first sweep generator after a number of sweep cycles equal to the number of tracked targets has been completed.

4. The system of claim'3 wherein:

the comparison means includes means for deducting from the second sweep generator output signal a 8 handling-time signal representative of the time required by the system to effect a defense against the target in the particular channel under consideration. 5 In a multiple target gun fire control system wherein targets are selected on the basis of the closing-time between the target and the gun, a target finder and comparator circuit comprising:

a sweep generator for developing cycles of negative-topositive voltage; a plurality of finder networks; each finder containing a voltage representative of the closing-time of a particular tracked target, and being responsive to the output of the sweep generator to provide a finder output in each cycle upon the summation of the sweep voltage and the closing-time voltage being zero; means controlled by each finder output for blocking further sweep in that cycle, for initiating a comparator sweep voltage which will clamp at a magnitude equal to the closing time voltage of that particular finder and for initiating the operation of a time delay gating circuit responsive to a finder output to limit the time for target consideration in each cycle; a plurality of comparator networks, corresponding respectively to said finder networks, for receiving the clamped comparator sweep voltage and closing-time voltages for any untracked targets detected by the system; each said comparator having means to deduct a voltage from the clamped comparator sweep voltage representative of the handling time for effecting an attack upon a particular tracked target; each comparator network being triggered when the closing-time voltage of a particular untracked target is less than the clamped sweep voltage minus the handling time voltage for a particular tracked target; said time delay gating circuit being operable when said tracked target has a smaller closing-time than the particular untracked target being compared whereby a new cycle may be started to consider another untracked target. 6. The multiple target gun fire control system of claim 5 further comprising a monitor network connected tothe sweep generator for initiating a new cycling sequence of the sweep generator after sweep cycles have been completed for all tracked targets;

whereby the closing-time of all tracked targets is compared in their order of greatest closing-time with untracked targets to provide signals to maintain the tracking of targets having least closing-time.

References (Cited by the Examiner UNITED STATES PATENTS 2,413,440 12/46 Farrington 250-27 MALCOLM A. MORRISON, Primary Examiner.

N. H. EVANS, F. M. STRADER, Examiners. 

1. IN A MULTIPLE TARGET GUN FIRE-CONTROL SYSTEM, WHEREIN TARGETS ARE SELECTED ON THE BASIS OF THE CLOSING-TIME BETWEEN THE GUN AND THE TARGET, THE COMBINATION OF: MEANS FOR PRODUCING A VOLTAGE REPRESENTATIVE OF EACH TARGET UNDER CONSIDERATION, THE AMPLITUDE OF EACH VOLTAGE BEING INDICATIVE OF THE CLOSING-TIME BETWEEN A PARTICULAR TARGET AND THE GUN; MEANS FOR COMPARING THE AMPLITUDE OF SAID VOLTAGES, AND MEANS FOR SELECTING THE VOLTAGE WITH THE SMALLEST AMPLITUDE, THEREBY INDICATING WHICH OF THE TARGETS UNDER CONSIDERATION HAS THE SMALLEST CLOSING-TIME. 